Transmission of vibration caused by unbalance in an aircraft engine with active control strategies

This work was initiated by the ideas of employing active systems inside the aircraft engine to actively reduce the vibration transmitted from the engine into the fuselage. Focusing on the vibration caused by the rotor unbalance and the comfort inside the fuselage, potential positions for actuators were identified along the vibration transmission path from the rotor to the fuselage: (1) at the bearing of the rotor, (2) inside the struts or along the links of the internal suspension of the engine, and (3) along the links of the mount system between the engine and the fuselage. To evaluate the active systems with these three actuator placement approaches, a model generation procedure was developed and state space models of different bearing configurations were created from this model. Three suspension systems were defined according to these actuation approaches, and their performances and different control strategies were compared based on the optimization results, which were generated in the frequency domain by minimizing different cost functions. Subsequently, several control algorithms (LQR, IFF & FxLMS) were investigated on four active systems: three systems corresponding to the three actuation approaches in which actuators and sensors were collocated and one system with the second approach controlling the vibration on the fuselage. The conclusions based on numerical results were discussed and most of them were verified by comparing them with those in past studies, in which the same methods were applied or similar systems were under investigation. At the end, suggestions were given for the selection and packaging of actuators, the selection and placement of sensors and the implementation of controllers.